Implantable neurostimulators are used to deliver neurostimulation therapy to patients to treat a variety of symptoms or conditions such as chronic pain, tremor, Parkinson's disease, epilepsy, incontinence, or gastroparesis. Typically, implantable neurostimulators deliver neurostimulation therapy in the form of electrical pulses via leads that include electrodes. To treat the above-identified symptoms or conditions, for example, the electrodes may be located proximate to the spinal cord, pelvic nerves, or stomach, or within the brain of a patient.
A clinician may select values for a number of programmable parameters in order to define the neurostimulation therapy to be delivered to a patient. For example, the clinician may select a voltage or current amplitude and pulse width for a stimulation waveform to be delivered to the patient, as well as a rate at which the pulses are to be delivered to the patient and a duty cycle. The clinician may also select as parameters particular electrodes within the electrode set carried by the leads to be used to deliver the pulses, and the polarities of the selected electrodes. A group of parameter values may be referred to as a program in the sense that they drive the neurostimulation therapy to be delivered to the patient.
Typically, a clinician selects parameter values for a number of programs to be tested on a patient during a programming session using a programming device. The programming device directs the implantable neurostimulator implanted in the patent to deliver neurostimulation according to each program, and the clinician collects feedback from the patient, e.g., rating information, for each program tested on the patient. The clinician then selects one or more programs for long-term use by the implantable neurostimulator based on the rating information. Some programming devices automatically present programs defined by the clinician to the INS, and collect feedback from the patient. One such programming device is described in U.S. Pat. No. 6,308,102, issued to Sieracki et al., which is incorporated herein by reference in its entirety.
Implantable neurostimulators typically include a nonrechargeable battery that provides power for delivery of neurostimulation. The longevity of the battery depends on the parameters of the program selected by the clinician for long-term delivery of neurostimulation. In particular, the battery longevity is inversely proportional to the pulse amplitude, pulse rate, pulse width, and duty cycle specified by the program, and to the load presented to the battery. Generally speaking, the load presented to the battery depends on the number of electrodes specified by the program for delivery of neurostimulation.
When the battery of an implantable neurostimulator is depleted, the implantable neurostimulator must be explanted from the patient and replaced. Replacement of an implantable neurostimulator is costly, and because it requires a surgical procedure the patient incurs risks associated with surgery. Nonetheless, clinicians typically do not consider battery longevity, e.g., the amount of time an implantable neurostimulator will be able to deliver neurostimulation according to a program before its battery expires, when selecting programs from among those tested during a programming session. This is despite the fact that battery longevities can vary greatly among the programs tested, e.g., from on the order of months up to two or more years.